A study on L-threonine and L-serine uptake in Escherichia coli K-12

A - Papers appearing in refereed journals

Khozov, A. A., Bubnov, D. M., Plisov, E. D., Vybornaya, T. V., Yuzbashev, T., Agrimi, G., Messina, E., Stepanova, A. A., Kudina, M. D., Alekseeva, N. V., Netrusov, A. I. and Sineoky, S. P. 2023. A study on L-threonine and L-serine uptake in Escherichia coli K-12. Frontiers in Microbiology. 14, p. 1151716. https://doi.org/10.3389/fmicb.2023.1151716

AuthorsKhozov, A. A., Bubnov, D. M., Plisov, E. D., Vybornaya, T. V., Yuzbashev, T., Agrimi, G., Messina, E., Stepanova, A. A., Kudina, M. D., Alekseeva, N. V., Netrusov, A. I. and Sineoky, S. P.
Abstract

In the current study, we report the identification and characterization of the yifK gene product as a novel amino acid carrier in E. coli K-12 cells. Both phenotypic
and biochemical analyses showed that YifK acts as a permease specific to L-threonine and, to a lesser extent, L-serine. An assay of the effect of uncouplers and composition of the reaction medium on the transport activity indicates that
YifK utilizes a proton motive force to energize substrate uptake. To identify the remaining threonine carriers, we screened a genomic library prepared from the yifK-mutant strain and found that brnQ acts as a multicopy suppressor of
the threonine transport defect caused by yifK disruption. Our results indicate that BrnQ is directly involved in threonine uptake as a low-affinity but high-flux transporter, which forms the main entry point when the threonine concentration
in the external environment reaches a toxic level. By abolishing YifK and BrnQ activity, we unmasked and quantified the threonine transport activity of the LIV-I branched chain amino acid transport system and demonstrated that LIV-I contributes significantly to total threonine uptake. However, this contribution is likely smaller than that of YifK. We also observed the serine transport activity of LIV-I, which was much lower compared with that of the dedicated SdaC carrier, indicating that LIV-I plays a minor role in the serine uptake. Overall, these findings allow us to propose a comprehensive model of the threonine/serine uptakesubsystem in E. coli cells.

KeywordsEscherichia coli; L-threonine uptake; L-serine uptake; Transmembrane transport; Amino acid transporter
Year of Publication2023
JournalFrontiers in Microbiology
Journal citation14, p. 1151716
Digital Object Identifier (DOI)https://doi.org/10.3389/fmicb.2023.1151716
Open accessPublished as ‘gold’ (paid) open access
Publisher's version
Output statusPublished
Publication dates
Online21 Mar 2023
Publication process dates
Accepted01 Mar 2023
PublisherFrontiers Media SA
ISSN1664-302X

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